Aggregation behavior of cetyldimethylethylammonium bromide under the influence of bovine serum albumin in aqueous/electrolyte solutions at various temperatures and compositions: conductivity and molecular dynamics study

Md Farid Ahmed; Mohammad Robel Molla; Mousumi Saha; Imrul Shahriar; Mohammad Saidur Rahman; Mohammad A Halim; Malik Abdul Rub; Md Anamul Hoque; Abdullah M Asiri

doi:10.1039/c9ra00070d

Aggregation behavior of cetyldimethylethylammonium bromide under the influence of bovine serum albumin in aqueous/electrolyte solutions at various temperatures and compositions: conductivity and molecular dynamics study

RSC Adv. 2019 Feb 25;9(12):6556-6567. doi: 10.1039/c9ra00070d. eCollection 2019 Feb 22.

Authors

Md Farid Ahmed^{1

2}, Mohammad Robel Molla^{1

2}, Mousumi Saha³, Imrul Shahriar³, Mohammad Saidur Rahman^{1

4}, Mohammad A Halim³, Malik Abdul Rub^{5

6}, Md Anamul Hoque¹, Abdullah M Asiri^{5

6}

Affiliations

¹ Department of Chemistry, Jahangirnagar University Savar Dhaka-1342 Bangladesh ahoque_ju@yahoo.com ahoque_ju@juniv.edu +880-2-7791052 PABX: +880-2-7791045-51 extn 1437.
² Bangladesh Council of Scientific and Industrial Research (BCSIR) Dhaka Bangladesh.
³ Division of Quantum Chemistry, The Red-Green Research Centre, BICCB Dhaka Bangladesh.
⁴ Department of Chemical Engineering, Faculty of Engineering, University of Malaya 50603 Kuala Lumpur Malaysia.
⁵ Chemistry Department, Faculty of Science, King Abdulaziz University Jeddah-21589 Saudi Arabia.
⁶ Center of Excellence for Advanced Materials Research, King Abdulaziz University Jeddah 21589 Saudi Arabia.

Abstract

Herein, we have investigated the interaction of bovine serum albumin (BSA), the most abundant globular protein, with a conventional cationic surfactant, cetyldimethylethylammonium bromide (CDMEAB), through a conductivity technique in the absence/presence of electrolyte solutions at various temperatures (298.15-323.15 K). The interaction of the protein with drugs/surfactants and other additives plays a crucial role in the body. Hence, the main concern of the study is to extract the impact of BSA on surfactant molecules and vice versa. From the specific conductivity versus concentration of surfactant plots, three different noticeable critical micelle concentration (c*) values were obtained for pure CDMEAB and its mixture with protein/protein + salts. The presence of BSA and electrolytes altered the c* values of CDMEAB revealing interactions among the studied constituents where the salt solutions reduced the c* values and created a convenient environment for favorable micellization. The negative magnitudes achieved for standard free energy changes (ΔG ⁰ _m) suggest spontaneity of micellization while the values of ΔH ⁰ _m and ΔS ⁰ _m signified the existence of some electrostatic and hydrophobic interactions. The values of molar heat capacity (ΔC ⁰ _m) were positive as well as small which was an indication of less structural deformation. Molecular Dynamics (MD) simulation for all atoms revealed that the salt ions promoted non-covalent interaction between BSA and CDMEAB, and such interactions were not observed in the absence of the salt. Protein structure remained nearly same in spite of strong interaction with CDMEAB as evident from the overall RMSD (root-mean-square deviation) values of the alpha carbons and backbone of the protein and RMSF (root-mean-square fluctuation) values of the amino acid residues present in BSA. In this work thermodynamic parameters of transfer (such as ΔG ⁰ _m.tr., ΔH ⁰ _m.tr., and ΔC ⁰ _p.m.tr.) were also evaluated and the results are discussed in detail. Besides, contributions of enthalpy and entropy to free energy changes were also analyzed.